1. Field of the Invention
The invention relates to a backflush filter with several filter chambers which receive filter inserts which can be flushed back by means of a flush filtrate loaded with compressed air, with a filter housing, a backflush device rotatably mounted in the housing around a rotary axis which backflush device comprises a filtrate pipe connection and a mud drain connecting piece, whereby, for the backflush, the filtrate pipe connection can be brought into fluid communication with a filtrate chamber of respectively one of the filter chambers which are arranged concentrically around the rotary axis and simultaneously the mud drain connecting piece can be brought into communication with a mud chamber of the respectively one filter chamber, further with a pressure chamber for flush gas and a flush valve closing this or releasing it to the filtrate pipe connection, and with a mud outlet and a mud drain valve closing this or releasing it to the mud drain connecting piece.
2. Description of Related Art
Such a backflush filter is for example known from EP 0361217 B1. This known backflush filter is comparatively complicated in its design, it has in particular a relatively large installation height, which can be ascribed amongst others to the fact that the mud drain valve and the drive actuating it is flanged to the actual filter housing at the bottom, while the flush valve with its associated drive projects upwards from the filter housing. The use of two separate drives for the mud drain valve and the flush valve makes it necessary to provide a sequence control unit for these two valves which ensures that the flush valve is only opened after the opening of the mud drain valve, so that, at the start of the backflushing, the fluid pressure on the mud side of the filter inserts is broken down before the backflush process is initiated. With a breakdown of this sequence control unit, an orderly cleaning of the filter inserts is not ensured, which can possibly go unnoticed for a longer operating time of the backflush filter.